Electropneumatic brake



T. H. THOMAS ELECTROPNEUMATIG BRAKE Filed April-11, 1928 Sept. 23, 1930.

ATTORNEY above type brakes or more Patented Sept. 23, 1930 UNET@ STATES Param' ori-Icey THM'AS H. THOMAS, 0F DGEWOOD, PENNSYLVANIA, ASSIGNOR TO THE WESTING- HO'SE AIR BRAKE COMPANY, OF PENNSYLVANIA on wILMEnDiNG, PENNSYLVANIA, A CORPORATION ELECTRO'PNEUMATIC :BRAKE Application filed April 11,

This invention relates to electro-pneumatic brakes and in particular to the type in which the brakes may be controlled either electrically or pneumatically.

One object of my invention is to provide an improved brake equipment of the above type, having means for causing an emergency application oi the brakes to be effected electrically on a train in case either an electric or pneumatic emergency occurs on any car in said train, when the brakes are in electric release position.

Another object of my invention is tok provide an improved brake equipment of `the in which the brakes may be pneumatically released after an electric emergency application and may then be pneumatical'ly controlled in the usual well known manner.

Another object of my invention is to provide an improved brake equipment ol the above type in which the control may be changed from electric to pneumatic, without causing an emergency application of the specifically an equipment in which a locomotive having means for electrically controlling the brakes may be cut oil l'rom a train and another locomotive may then be connected to said train, without having to cause an emergency application of the brakes.

Other objects and advantages will appear in the following more detailed description of my invention.

In the accompanying drawing, the single figure is a diagrammatic view, partly in secl tion, oit' an electro-pneumatic brake apparatus embodying my invention.

As shown in the drawing, the brake ap paratus comprises a combined electric con-k trol and selector valve portion 1 and a triple valve portion 2 mounted on the opposite sides ot' a bracket 3 to which is also connected a vent valve device 4, an auxiliary reservoir v`5, an emergency reservoir 6, a brake cylinder 7, and a quick action reservoir 8.

The combined electric control and selector valve portion 1 comprises a magnet 9 connected in a train wire and adapted to control the operation of two independently 1928. Serial No. 268,102.

movable armatures 11 and 12. The arma-V ture 11 has a stem 13 extending downwardly through a central opening formed in the magnet core 14 and interposed between `said armature and the upper face of the core 14 is a spring 15 tending to shift the armature 11 upwardly'and thereby resist the magnetic pull of the magnet 9 when energized.l The magnet armature 12 is slidably mounted in a suitable bore in the casing and is' engaged by one end of a push rod 16 slidably extending through a central bore in the armature stem 13. rlhe opposite end ot said push rod terminates in a cavity 17 formed in the upper end of said armature stem and has secured thereto a` collar 18. A spring 19 is interposed between the upper faceY of said collar and a capv nut 20 having screw-threaded engagement in the casing, said spring tending to shift the armature 12 downwardly, so that when the magnet is energized, the force of said springopposes the magnetic pull be-' tween said armature anda flange 21 formed at the lower end of the armature stem 13.

' A flexible diaphragm 22 is mounted` between a shoulder 23 on the casing wall and an apertured member 24 having screwthreaded engagement in the casing wall. Said diaphragm forms at one side a chamber 25, and at the opposite side a chamber 28. Centrally carriedby thef diaphragm 22 is a' valve seat 29 having a'hollow sleeve-like extension30 adapted to be secured ture 12 by screw-threaded engagement. In order to clamp the diaphragm against the seat 29 and thereby maintain the relative operative position of said diaphragm' and the armature 12, an external sleeve 3l is interposed between a shoulder formed at the back of valve seat 29,v adjacent theyextension 30, and the lower face of the armature 12 and is 4adapted to loosely operate through the aperture in member 24. l

A valve 32, contained in chamber 28, has a tinted stem extending into a chamber 33 formed in the valve sleeve 30, and is adapted to control communication between chambers 28 and 26 through said chamber 33 and ports 34 in the side wall of sleeves 30 and 31. A spring 35, contained in the chamber 33 in sleeve 30 acts on the tition wall and into a chamber 42, wherein a spring 43 acts on a washer 44 in engagement with said valve stem andurges said valve to its upper seated position, as shown in the drawing. Said valve has a tluted stem 45 at the upper side which extends through a par tition wall and into a chamber 46, which is connected to the atmosphere through a passage 47. Said valve is adapted to be operated by one arm ot a lever 48 which is fulcrumed on a fixed pin 49 secured in the casing. The opposite arm ot said lever is adapted to be engaged by a shoulder 50 on the armature stem flange-21, so that upward movement of the armature 11 causes the lever 48 to rotate and seat the double beat valve 39 in its downward position against the pressure of spring 43.

The selector valve portion comprises a piston 52, contained in a chamber 53, which is connected to the magnet double beat valve chamber 40 through a passage 51, and a slide valve 54 contained in a chamber 55 and adapted to be operated by said piston, which piston is opposed in moving outwardly by a spring 111 in chamber 53.

An'emergency switch 56 is Vcontained in a chamber 57 and is adapted to normally bridge two contacts 58 mounted in an apertured wall 59 separating chamber 57 from a chamber 60. `The train wire 10 is connected to the contacts 58, so that the magnet and .switch are connected in line.

The switch 56 is operatively connected to a pist-on 61 by a stem 62, said piston having at one side a chamber 63 and at the opposite side a chamber 64, which contains a spring 65 urging the. piston 61 upwardly, thereby7 tending to maintainthe switch 56 in engagement with the contacts 58.

A double beat valve 66 is contained in a chamber 67 and has at one side a fluted stem 68 extending through a suitable bore in the casing and into a chamber 69, wherein a spring 70, acting on a collared stem 71 in engagement with the valve stem 68, tends to seat the valve 66 in its upper position, as shown in the drawing. Sia-id valve has at the opposite side a fluted stem 72 extending through a suitable bore in the casing and into chamber 57 in axial alignment with an extension 73 of the switch stem 62, sothat downward movement ot the switch causes Yvalve piston 7 8 having the extension 73 to engage the valve stem 72 and seat the double beat valve 66 in its lower position against the resistance of spring 70.

Contained in a bore in the casing is a high pressure valve piston 74 having at one side a chamber 75 containing a spring 76 tending to seat said valve piston against a seat ring 77. Contained in another bore in the casing is a at one side a chamber 79 containing a sprin 80 urging said valve piston upwardly towarda seat ring 81 formed in the casing.

The triple valve device 2 comprises a casing havingl a piston chamber 82 connected to the usual brake pipe 83 and containing a piston 84, and a valve chamber 85 connected to the auxiliary reservoir 5 through passage and pipe 86 and containing a main slide valve 87 and an auxiliary slide valve 88 adapted to be operated by said piston. The quick action portion ot the triple valve device comprises the usual quick action piston 89, having at one side a chamber 90 and at the opposite side a chamber 91 connected to the brake cylinder 7 through passage and pipe 92, and a ventvalve 93 contained in a chamber 94 and adapted to be operated, by said quick action piston. The usual check valve 95 is also contained in chamber 94.

The vent valve device 4 comprises a piston 96 having at one side a chamber 97 and at the opposite side a chamber 98 connected to the atmosphere through a passage 99, and a vent valve 100 contained in a chamber 101 and adapted to be operated by said piston. A spring 102 tends to hold the vent valve 100 seated against the seat ring 103 formed in the casing.

A brake switch and brake valve device (not shown) are located in the locomotive, and the brake switch is operable independently ot the brake valve. The brake switch is adapted to vary the strength of the current liow through the train wire 10 and magnet 9. When the current is suciently strong, the magnetic pull on the armature 11 is such as to move said armature downwardly against the pressure of spring 15, thereby shitting` the armature stem 13 and flange 21 downwardly and permitting spring 43 to seat the double beat valve 39 in the upper position. The magnetic pull on the armature 12 tends to overcome the opposing pressure ol spring 19 and shift the armature 12 upwardly to a position in which the valve 104 is seated by spring 38, and valve 32 is unseated by spring 35. The brake valve device may be of the usual well known type which is adapted to control the fluid under pressure in the brake pipe 83.

Fluid under pressure supplied to the brake pipe 83 flows therefrom through chamber 105 and passage 106 to the triple valve pistou chamber 82, wherein said pressure acts upon the piston 84, thereby shitting said piston `valve 104 is seated and and the slide' valves 87 and 88 to release position, as shown in the drawing. The valve chamber 85 is then charged through the bypass passages 107 and' 108, and the auxiliary lreservoir 5 is charged from said valve chamber through passage and pipe 86.

`F luid under pressure also flows from the pistonV chamber 82 through passage 107, past the ball check valve 109 and through passage and pipe 110 to the selector valve chambe155, the magnet valve chamber 36, valve spring chambers 42 and 69 and to the upper face of the high pressure valve piston 74, outside of the seat ring 77.

Vith the apparatus in the electric release 1 position, and the magnet 9 therefore fully energized, the magnet double beat valve 89 is seated in the upper position, the magnet the magnet valve 32 is unseated. Vith the double beat valve'39 seated in the upper position, fluid under pressure flows from spring chamber 42 pastthe fluted stem 41 of said valve, through chamber and passage 51l to the 'selectorpiston champressures thus equalize on.

ber 53. The fluid the opposite sides of vthe selector piston 52,

and spring 111 shifts said piston and slide .114 in the selector and pipe 115.

valve 54 to their inner position, in whichthe quick action reservoir 8 is charged with fluid at auxiliary reservoir pressure by flow from the triple Vvalve chamber 85 through port 112 in the main slide valve, passage 113, cavity slide valve 54 and passage lith the selector slide valve 54 in the inner position, the brake cylinder 7 is connected to the atmosphere through pipe and passage 92, cavity 116 in the selector slide valve 54, passage 117, magnet valve chamber 28, past the unseated valve 32 and from thence through chamber 33, ports 34 through the side walls of sleeves 30 and 31, chamber 24 and the atmospheric passage 27. The

quick action piston chamber 91 and chamber 90 which is connected to chamber 91 past they loosely fitted piston 89, in addition to valve piston chamber 79 and the upper face of the high pressure valve piston 74 inside the seat ring 77, are all connected to the brake cylinder passage 92 and therefore vented to the atmosphere, when the brake cylinder is vented as above described. K

The vent valve piston chamber 97 is connected through pipe and passage 118 to the emergency switch piston chamber 68 and both are vented to the atmosphere through port 119 in the switch piston 61, chamber 64, port 120 in the casing wall, chamber 60, through the aperture in wall 59, chamber 57 and an atmospheric passage 121. The pressure of spring 102 therefore is permitted to hold the vent valve 100 seated and the pressure of spring holds the switch piston 61 in its the emergency reservoir 6,

lthrottles the rtive in valve chamber 28 With the switch piston 61 and switch 56 in their upper position,as shown in the drawing, spring 70 seats the double beat valve 6e e 1n its upper position, so that fluid at emergency reservoiry pressure flows from the chamber 69 through` chamber 67, and passage 123 to chamber at the lower side of the high pressure valve piston 74, thereby permitting spring-76 to hold saldvalve piston seated againstthe seat ring 77 and thus prevent the iiow ofiiuid at emergency reservoir pressure from passage 1.10 tothe brake Acylinderpassage 92, which is vented to the atmosphere. If it is desired to effect a service application of the brakes, the strength of the current flow through the train wire 10 is reduced, thereby vreducing the pull of magnet 9, so that thel pressure of spring 19, acting on the push rod16, shifts the armature 12 downwardly, thereby causing the valve seat 29 to rst enthe valve 32 and close communication between chambers 28 and 26 and then unseat the valve 104, so as to permit fiuid at emergency' reservoir pressure tol flow from the valve chamber 86 to the brake Cylinder 7 by way of valve chamber 28, passage 117, cavity 116 in the selector slide valve 54 and passage and pipe 92, and thereby apply the brakes. l/Vhen effecting an electric service applica.- tion of the brakes, the usual brake valve device is left'in running position, so that the brake pipe pressure i's maintained and the triple valve remains in release `posit-ien, in which communication is established between the brake pipe 83, auxiliary reservoir 5, and the emergency 'reservoir 6, through passages 107, A108, and 110,-as hereinbefore described. Consequently, as fiuidunder pressure flows from the emergency reservoir to the magnet valve` chamber 28 and from thence to the brake cylinder 7, the emergency reservoir pressure'tends to be maintained by flow of iiuid 'under pressure from said brake pipe and auxiliary reservoir. If such flow through passage 107 tends to reduce the brake pipe pressure in the triple valve piston chamber 82 at a Jfaster rate than the auxiliary reservoir pressure reduces through passage 108, the triple valve'piston 84 moves outwardly and passage 107, so as to prevent a suilicient pressure differential from' building up on said `'piston to' shift the slide valves 8' and 88. As a result,in electric service-operation the triple valve is maintained in the release position. v

If it is desired to limit the degreeof brake cylinder pressure in an electric service application to some `degree less than the pressure in the emergency reservoir, the reduction in strength of the current in the train'wire is limited to any amount desired. Then, when the brake cylinder-pressure, which -is effecupon the diaphragm 22, becomes sufficient to overcome the pressure of spring 19, said diaphragm is deflected upwardly and permits spring 38 to seat valve 104 so as to prevent further flow of fluid under pressure from chamber 36 to chamber 28 and the brake cylinder 7.

In order to release the brakes after an electric service brake application, the current strength in the train wire is built up again to a degree sufficient to unseat the valve 32 and thereby permit fluid under pressure to flow from the brake cylinder 7 tothe atmosphere and at the same time the apparatus is recharged in the same manner as hereinbefore described.

If it is desired to electrically effect an emergency application of the brakesthe brake valve (not shown) is moved to lap position and the brake switch (not shown) is then operated so as to cut off the` supply of electric current to the train wire 10. The magnet 9 thereby is totally deenergized and the pressure of spring 19 operates the armature 12 to seat valve 32 and unseat valve 104, in the same manner as in a service application of the brakes, as hereinbefore described. With the magnet totally deenergized, however, the pressure of spring 19 maintains the valve 32 seated and valve 104 unseated.

With the magnet totally deenergized, spring 15 shifts the armature 11 upwardly, thereby causing the armature stem flange 21 to engage and rotate the lever 48, so as to seat the double beat valve 39 in the lower position against the resist-ing pressure of spring 43. The spring chamber 42 is thereby disconnected from valve chamber 40 and the latter chamber is vented to the atmosphere past the fluted valve stem 45, through chamber 46 and the atmospheric 'passage 47. The selector valve piston chamber 53 being connected through passage 51 to valve chamber 40, fluid under pressure is vented therefrom to the atmosphere, so that the pressure of the fluid in the selector valve chamber 55 then shifts the selector piston 52and slide valve 54 to the outer position, against the pressure ol spring 111.

In the outer position of the selector slide valve 54, fluid under pressure flows from the quick action reservoir 8 to the vent valve piston chamber 97 and the emergency switch piston chamber 63 by way of pipe and passage 115, cavity 114 in the selector slide valve 54 Vand passage and pipe 118.

The pressure of the fluid in the switch piston chamber 63 shifts the piston 61 downwardly against spring 65 and causes the switch 56 to first disconnect the two train wire contacts 58. Further downward movement of said piston then shifts the double beat valve 66 to the lower position on account of engagement of the switch stem extension 73 and the iluted valve stem 72. Y

'With the double beat valve 66 seated in the lower position, communication is closed between chambers 69 and 67 and the high pressure valve piston chamber 75 is vented to the atmosphere through passage 123, valve chamber 67 ,past the fluted valve stem 72, through chamber 57 and the atmospheric passage 121. The pressure of the fluid fromthe emergency reservoir 6 acting on the upper face of the high pressure valve piston 74, outside of seat ring 77, then shifts said valve piston to its downward position against-.the pressure of spring 76. Fluid under directly from the emergency reservoir 6 to the brake cylinder 7 through pipe and passage 110, past the unseated high pressure valve piston 74 and through passage and pipe 92. The rate of flow and the consequent rate of build up of brake cylinder pressure under such a condition is more rapid than the rate of build up in a service application of vthe brakes.

At the same time as the is operated, the vent valve piston is also shifted downwardly by fluid under pressure from the quick action reservoir 8, and unseats the vent valve 100, thereby permitting the fluid under pressure to be vented from the brake pipe 83 through chamber 101, chamber 98 and the atmospheric passage 99. This complete venting of the brake pipe is ossible, since when an electric emergency application of the brakes is effected by movement of the brake switch (not shown), the brake valve (not shown) is moved to lap position, in order to cut off the supply of fluid under pressure to the brake pipe, as hereinbefore described.. y

Since the triple valve piston chamber 82 is connected to the brake pipe 83 through passage 106 and chamber105, the fluid under pressure is vented therefrom, thereby permitting the pressure of the fluid in the slide valve chamber 85 to shift the piston 84 and slide valves 87 and 88 to their outward or emergency position, in which port 125 in the main slide Valve registers with the brake cylinder passage 92 and thereby permits fluid under vpressure to flow from the auxiliary reservoir 5 and valve chamber 85 to the brake cylinder.

In emergency position of the triple valve slide valve 87, a passage 126 is uncovered, so that fluid under pressure is also permitted to flow from valve chamber 85 to the quick action piston chamber 90. However, since the chamber 91 at the opposite side of the quick action piston is connected through passage 92 to the brake cylinder, wherein a pressure is rapidly built up through the operation of the high pressure valve piston 74 ahead of the operation of the triple valve device, the brake cylinder pressure reacting on piston 89 prevents said piston from being operated by the pressure in chamber 90. The operation of the usual quick action portion switch piston 61 of the triple valve, including the piston 89, will be hereinafter described.

It is evident from the above description that an electric emergency application of the brakes can be effected at any time, even while a service application of the brakes is being effected, and that the apparatus will operate to cause the brake cylinder pressure to be built up rapidly. y

It Vwill further be evident that failure of the electric current, as due to the breaking of a train wire, will cause an emergency brake application in the vsame manner as if the current supply is manually cut olf.

In order to release the brakes after an electric emergency application, the brake valve (not shown) is operated in such a manner as to recharge the brake pipe with fluid under pressure. The brake'switch (not shown) is also operated to supply the required current to the magnet 9. The magnet then operates to vent the fluid under pressure from the brake cylinder andthe apparatus is re-L charged with fluid under pressure inthe same manner as in'initially charging, as hereinbefore described.

If, while the brake apparatus is in the electric release position, thefluid under pressure is suddenly vented-from the brake pipe, as may be caused by the rupturing of the train pipe 83 or by the bursting of a brake pipe hose, an emergency application of the brakes is initiated pneumatically by the brake apparatus nearest the point of venting, which apparatus then operates to electrically cause an emergency brake application on the train, in the following manner.

The sudden venting of the brake pipe causes the triple valve to operate and supply lluid under pressure to the brake cylinder 7 in the same manner as hereinbefore described, and at the same time to permit Huid under pressure to flow to the quick action pisl'ton chamber 90, thereby shifting the vquick action piston 89 downwardly and unseating the valve 93. Fluid under pressure from the brake pipe 83 then raises the check valve 95 and flows through chambers 94 and 91 'and' passage 92 to the brake cylinder and thereby causes a local venting of fluid under pressure from the brake pipe in the usual well known manner'. f

Fluid under pressure also flows from the quick action piston chamber 90 througlrpassage 127 to the upper face of the valve piston 78 outside of the seat ring 81.. Since the chamber 79 at the opposite side of said valve piston is connected to the brake cylinder passage 92, and at the initiation of this brake application is at substantially atmospheric pressure, the pressure of the fluid from passage 127 shifts said valve piston to its downward position. Fluid under pressure then flows from passage 127 to passage 128 and from thence through cavity 129 in the selector slide valve 54 and passage and pipe 118 to the vent valve piston chamber 97 and emergency switch piston chamber 63. The switch piston 61is thereby operated and shifts the switch 56 away from the train wire contacts 58, thus opening' the circuit through the train wire 10, lwhich causes theI brakeapparatus on each carin the train to operate electrically and effect an emergency application of the brakes, in the same manner as hereinbefore described.

vAt the same time as the train wire switch 56 is opened, the vent valve 100 is unseated by the piston 96 due to the pressure of the fluid suppliedto th'episton chamber 97. Unseating of said vent valve effects a large opening from'the brake pipe to the atmosphere, so that if forv anyreason, the quick action portion of the triple valve device fails to operate and propagate quick action throughoutthe train in the usual manner, the operation of the vent valve 100 insures such quick action. .This is especially desirablein that if the switch' 56 fails to` open the train wire circuit in the car nearest the brake pipe rupture, the brake apparatus on the adjacent car or on a nearby car will be pneumatically operated and causes the train wire switch 56 on the car to operate and effect an electric emergency brake application. Itis obvious that if the electric switch on the car first mentioned operates properly that the serial venting of the brake pipe has no effect upon the brake application, however it is equally apparent that in order to ensure the maximum safety of the braking system, it is necessary that the brakes will be applied even though one controlling means fails.

If an electric-emergency application of the brakes occurs due to failure "of the electrical current for any reason, the brakes on the train may be released pneumatically, and then the train may proceed with the brakes pneumatically controlled'.

In order to pneumatically release the brakes after an electric emergency brake application, the brake pipe 83 is'recharged iny the'usualv manner. The triple valve is therej the saine manner as hereinbefore described.V

As in emergency, the selector piston 52 and slide valve 54 are in their outer position, since the magnet 9 vis deenergized, so that the venting of fluid under pressure from the brake cylinder 7 is controlled through the triple valve slide valve 87 by way of pipe and pas sage 92, cavity 130 in said slide valve, passage 131, cavity 132 in the selector slidevalve 54, and the atmospheric passage 133.

If it is desired to pneumatically effect a service application of the brakes when the brakes are being pneumatically controlled, the brake pipe pressure is gradually reduced in the usual well known manner. The triple valve piston 84 and slide valves 87 and 88 are then shifted to the usual service position in which fluid under pressure is permitted to flow from the auxiliary reservoir 5 to the brake cylinder 7 through the valve chamber 85, port 134 in the main slide valve 87 and passage and pipe 92, thereby applying the brakes.

If it is desired to pneumatically effect an emergency application of the brakes, the brake pipe pressure is suddenly vented in the usual manner, thereby causing the triple valve piston 84 to'shift the slide valves 87 and 88 to emergency position, in which fluid under pressure is permitted to iiow from the auxiliary reservoir 5 to the brake cylin der 7 and to the quick action piston chamber 90 as hereinbefore described. The quick action piston 89 then opens thev vent valve 93 to permit a sudden local venting of fluid under pressure from the brake pipe 83 and chamberf105 to the brake cylinder, and at the same time the .valve piston 78 is opened to permit fluid under pressure to flow to the vent valve piston chamber 97 and v'switch pis ton chamber 63. The vent valve 100'is thus opened in order to eect a suddenventing of fluid under pressure from the brake pipe to the latmosphere so as to propagate Jdie quick emergency action throughout the train, while the switch piston 63 shifts valve 66 downwardly and Vcauses the high pressure valve piston'74 to be operated, so as to permit fluid under pressure to flow from the emergency reservoir 6 to the brake cylinder 7 and thus cause a rapid application of the brakes..

In order to 'pneumatically release the brakes after a service or an emergency application thereof, the brake pipe 83 is recharged, thereby causing the triple valvey kdevice to return tothe release position in which the auXiliary reservoir 5 and emergency reservoir 6 are recharged, and fluid under pressure is vented'from the brake cylinder the atmosphere -in inbefore described. l

-If' it is'desired'to change locomotives on a train, as at a terminal, the brake vswitch (not shown) is left yin release position so that the magnets 9 remain fully energized. The brake valve (not shown) is then operated to effect a service reduction in brake pipe pressure, thereby causing thetriple valve to move toserviceposition, in which position fluid under pressure is permitted to flow from the auxiliary reservoir 5 to the brake cylinder' 7 and thus apply the brakes. At the sam'e time, the quick action reservoir 5 is vented to the atmosphere through pipe and passage 115, cavity 114 in the'selector slide valve 54, passage 113, cavity 135 in the triple valve slide valve 87, when in service position, and then through the atmospheric passage 136. After said quick action reservoir is thus vented, the

brakes.

Y 7 to the same manner asheren supply of current to the train wire 10 is cut off and the magnet 9 is thereby totally deenergized and operates yin the same manner as in electric emergency. The selector piston 52 and slide valve 54 are shifted to their outer position, in which the quick action reser# voir 8 is connected to the vent valve piston chamber 97 and to the emergency Yswitch piston chamber 63. The ventvalve device and emergency switch are not operated as in case of Van electric emergency however, since the quick action reservoirwas vented prior to deenergization of the magnet 9 and the consequent movement of the selector piston and slide valve.

With the triple valve in the usual service or service lap position and the magnet 9 deenergized, the locomotive may be cut off from the train. Another locomotive having means for electrically controlling the brakes may then be connected to the train, after which the brakes 'may be released by recharging the brake system and supplying the required electric current to the train wire 10 in the same manner, as hereinbefore described. If desired, the locomotive which is connected to said train, maybe adapted to cont-rol the brakes pneumatically only, in which case, the brake pipe will be recharged in the usual well known manner and thereby release the Said brakes may then be operated pneumatically in the same manner as hereinbefore described.

It is desirable to be thus able to change the locomotives on a train by effecting only a service application of the brakes, since where a train is long, less time and 'less compressed fluid are required to recharge the brake pipe than ifV a greater reduction ora total venting of the fluid under pressure from the brakey pipe is effected. l

While one illustrative embodiment of the invention has been described in detail, it is not my intention to limit its scope to that embodiment or otherwise than by the terms ofthe appended claims.

l-laving now described'my invention, what I claim as new and desire to secure by Letters Patent, is :-v l

1. In an electro-pneumatic brake, the combination with a brake cylinder, of valves for controlling the supply and exhaust of kfluid tofand from the brake cylinder in service, a magnet for operating said valves, a slide valve adapted in one position to establish communication through which fluid is supplied to the brake cylinder by operation of said electrically controlled valves, means operated in another position of said slide valve for effecting an emergency application of the brakes, a piston for operating said slide valve, and a valve operated by said magnet for varying the fluid pressure on said piston.

2. In an electro-pneumatic brake, the combination with a brake cylinder, of a valve for controlling the supply of fluid under pressure to the brake cylinder `to el'ect a service application of the brakes, a magnet for operating said valve, ed in one position to establish communication through Which said electrically controlled valve supplies fluid to the brake cylinder, means operated upon movement of said slide valve to another position for effecting an emergency application ton operated upon a reduction in fluid pressure for shifting said slide valve to its last mentioned position, and a valve operated by said magnet for venting fluid from said piston.

3. In an electro-pneumatic brake, the combination with a brake cylinder, of a valve for controlling the supply of fluid under pressure to the brake cylinder to effect a service application of the brakes, a magnet for operating said valve, a slide valve adapted in one position to establish communication through Which said electrically controlled valve supplies luid to the brake cylinder, means operated upon movement of said slide valve to another position for effecting an emergency application of the brakes, a piston operated upon a reduction in fluid pressure for shifting said slide valve to its last mentioned position, and a valve operated upon deenergization of said magnet for venti ing fluid from In testimony my hand.

said piston.

whereof I have hereunto set THOMAS H. THOMAS.

a slide valve adapt-` of the brakes, a pis- 

